There are some living things that you just don't expect to be made into Pokémon. I'm not holding my breath for a nematode Pokémon, or a tapeworm Pokémon, or a halophilic archaea Pokémon (though all of these would be fantastic). But even back in Generation I, there were a few very unlikely inspirations at work. A mind-altering parasitic fungus Pokémon?

Fungus seems to be associated with the Grass-type within the Pokémon universe, though in reality, fungi are neither plant nor animal, making up a third kingdom all of their own. Mushrooms are the most familiar member of the group, but microscopic organisms such as molds and yeast also fall under this category. Though they live stationary lives like plants, they have plenty in common with animals too. For instance, while plants make their own food via photosynthesis, fungi rely on other living things to produce food for them, just like animals do. This food is often dead plant and animal matter, but some species of fungus are more adventurous when it comes to obtaining nutrition. Many fungi are specialized parasites, and will live as unwelcome guests upon various other species of plants, animals (including us humans) and even other fungi. Some will actively devour their host, but in many cases it makes more sense to keep the host alive, ensuring a constant supply of food.

Last time, I talked about the Nincada family, based upon the cicada. But Nincada and its kin were, it would seem, actually the second family to draw inspiration from cicadas. For the first, we need look no further than Paras and Parasect, the Mushroom Pokémon. Specifically, both of these Pokémon seem to be based on the cicada nymph, the immature phase that accounts for most of their lives. They have the cicada nymph's powerful front claws, and Paras' Pokédex entries mention it living underground and getting nutrition from tree roots. Cicada nymphs of certain species also share Paras and Parasect's striking red color. But what of the mushrooms growing from them?

The Pokédex itself helpfully identifies these mushrooms as tochukaso. This is a real species of fungus, Cordyceps sinensis, commonly known as caterpillar fungus. This species actually preys upon the caterpillar-like larva of ghost moths in the genus Thitarodes. The fungus invades the bodies of larvae living in the soil, eventually killing them. The larvae die near the surface, and the fruiting body or 'mushroom' of the fungus ultimately bursts out of the larva's forehead, and can extend up to fifteen centimetres above the ground. The fruiting body spreads its spores, and its life cycle begins over again, with more larvae being infected by the new generation of fungus.

There are plenty of species of Cordyceps that infect a whole range of insects... so why was tochukaso referred to so specifically by the Pokédex? Well, this particular fungus is well known for its apparent medicinal properties. It has been used in traditional Chinese and Tibetan medicine for hundreds of years, to treat many different ailments, and also as an aphrodisiac. Scientific studies have suggested that there may indeed be medicinal benefits to ingesting tochukaso, with experiments on mice indicating possible uses as an antidepressant or treatment for diabetes. But one of tochukaso's most well-known uses is by Chinese athletes. In 1993, a suspiciously large number of records were broken by a track team at China's National Games. Anabolic steroids were suspected, but the athletes passed drug tests, and the coach claimed that their unusually good performance was due to taking tochukaso and turtle blood. However, it should be noted that the very same coach withdrew a number of his athletes from the 2000 Sydney Olympics at the last minute, leading many to suspect that he was afraid that the new, more accurate doping tests would have revealed what was really going on.

A Camponotus ant with Cordyceps erupting from its body (L. Gilbert, University of Texas).

Cordyceps fungus may or may not be beneficial to humans, but for insects, the effects are always disastrous. Each of the many thousands of Cordyceps species specialize in parasitizing a particular type of insect, and infections can wipe out whole colonies. For instance, Cordyceps cicadae, Cordyceps heteropoda and Cordyceps sinclairii all prey on different species of cicada. But some members of the Cordyceps genus take the invasion of their host's body a step further...

One example is Cordyceps unilateralis, which infects a particular species of ant, Camponotus leonardi. The fungus spreads through its host, but doesn't kill it straight away. It restricts itself to consuming the ant's non-vital tissues, until the time comes to release spores. At this point, it spreads into the ant's brain and alters the creature's perception. The ant is compelled to climb to the top of a tall stalk, and clamp on with its jaws. The fungus then finally kills its host, leaving it frozen in position. When the fruiting body emerges, the ant will have taken it into a prime position to release spores... and spread them to as many other ants as possible.

I started this column by expressing some surprise that such a grisly arrangement was chosen as the basis for a Pokémon family. But what's even more surprising is just how close to nature the Pokémon version is. The fruiting bodies may have been replaced by colorful cartoon mushrooms, but the basic process remains the same. The evolution from Paras to Parasect represents the point at which the fungus seizes control of the insect's brain, leading to Pokédex entries for Parasect like the following: "The bug host is drained of energy by the mushrooms on its back. They appear to do all the thinking" and, perhaps even creepier, "When nothing's left to extract from the bug, the mushrooms on its back leave spores on the bug's egg."

Many Pokémon will take a real species' characteristics and exaggerate them in some way, but the Paras family seems to have taken the Cordyceps-insect relationship and made it even more sinister. Rather than simply killing its host, the fungus infecting the creature essentially becomes its host. I always feel a little odd when allowing a Paras to evolve into Parasect, since I'm basically allowing its brain to be hijacked by another organism, turning it into a blank-eyed zombie Pokémon. I don't think there's a single more disturbing Pokémon family than this one, and unless Generation V surprises us with a parasitoid wasp Pokémon, I don't think there ever will be.

Join me again on Wednesday for a special Tanabata edition of On the Origin of Species, which I promise will feature no bugs or fungi, nor any combination thereof.